1. Preliminary Results: The Effect on Malaria Burden after a Change in Insecticide for Indoor Residual Spraying in Zimbabwe
Beth Brennan, Ben Johns, Allison Belemvire, Shadreck Sande, Dr. Joseph Mberikunashe, Elana Fiekowsky, Hieronymo Masendu
APHA 143rd Annual Meeting
November 3, 2015

2. No relationships to disclose
Disclosure Statement
Elana Fiekowsky
The following personal financial relationships with commercial interests relevant to this presentation existed during the past 12 months:
No relationships to disclose

3. Agenda
Background
Objective
Methods
Analysis
Limitations
Conclusions

4. PMI Africa Indoor Residual Spraying (AIRS) Project
President’s Malaria Initiative (PMI)
17 countries in Africa
Aug
Over 10m people protected, 3m structures sprayed, 10k people trained per year

5. Objective
The study is intended to assess if using organophosphates insecticides (OPs) in IRS has an effect on the number of confirmed malaria cases at health facilities (HFs).

6. Known Mosquito Resistance
Objective - 2
Table 1. Summary characteristics of intervention (OP) and comparison IRS districts
Analysis Group No.
Province
District
Insecticide Type
Known Mosquito Resistance 1
Manicaland
Mutare PY OP
PY, carbamates resistance
Chimanimani
No data
Mutasa
Nyanga 2
Buhera
DDT
Makoni
Chipinge 3
Mashonaland Central
(Comparison areas)
Bindura
Centenary
Guruve
Mazowe
Mbire
Mt Darwin
Shamva

7. Methods
Data was collected from 4 PMI-supported (OP) districts and compared to government-sprayed districts with PY and DDT insecticides.
Figure 1: Proportion of districts with missing data, by month

8. Results
Analysis 1. The number of confirmed malaria cases in health facilities in the four intervention districts in (PYs) and (OPs)
Results show a marked drop in the incidence of test positive cases in all ages associated with the change from PYs to OPs in the four PMI-supported intervention districts.
Figure 2: The number of test positive cases per 1,000 people diagnosed at HFs in the four intervention districts, by month and age category
* p < 0.05; ** p < 0.01

9. Results - 2
Analysis 1. The number of confirmed malaria cases in health facilities in the four intervention districts in (PYs) and (OPs)
Unadjusted results present a potential case for IRS with OP insecticide having an effect on malaria burden in these four districts. On average, in high transmission, the incidence rate of test positive cases per 1,000 people in 2015 was 38% of what it was in the same period in 2014 for all ages.
Table 2. The average number of test positive cases per month (per 1,000 people) diagnosed at HFs in the four intervention districts, by period and age category
Period
Age group
PY (2014) OP
(2015)
Unadjusted IRR
Mean
95% CI
p-value
January-June (high transmission)
U5s
5.4
2.1
0.39
0.22 to 0.68
0.001**
All
30.6
11.5
0.38
0.22 to 0.66
February-April (peak transmission)
7.5
2.7
0.36
0.17 to 0.78
0.01*
45.6
15.6
0.34
0.17 to 0.71
0.004**
* p < 0.05; ** p < 0.01

10. Results - 3
Analysis 2. The number of confirmed malaria cases in HFs in 4 intervention districts in (PYs) and (OPs) to 10 other districts
Figure 3. The number of test positive cases per 1,000 people diagnosed at health facilities, by comparison
group, month and all ages
IRS

11. Results - 4 Analysis 2 cont.
Figure 4. The number of test positive cases per 1,000 people diagnosed at health facilities, by comparison group, month and children under 5 years of age

12. Results - 5 Analysis 2 Cont.
Table 3. The number of test positive cases per 1,000 people diagnosed at health, by comparison category, period, and age category
Area
For January to June high transmission period
For February to April peak transmission period
2013/14
2014/15
Risk difference
Unadjusted IRR
All ages
Known resistance, switch to OPs in 14/15
30.6
11.5
19.1*
0.38**
45.6
15.6
30.0*
0.34**
Other Manicaland
17.6
7.5
10.1*
0.43**
24.8
9.1
15.7*
0.37*
Mash Central comparison areas
21.0
12.4
8.6*
0.59*
28.0
15.0
13.0
0.54*
Children under 5 years of age
5.4
2.1
3.3*
0.39**
2.7
4.8
0.36*
3.0
1.2
1.8*
0.40**
4.1
1.4
2.7*
0.34*
3.2
1.1
0.66
4.0
2.5
1.5
0.62

13. Limitations These are preliminary unadjusted results
Results do not control for other factors (i.e. other malaria interventions, individual districts, data reporting, month of peak season, etc.)
Questionable data quality and limited time frame for analysis

14. Conclusions
Decline in malaria burden reported to HFs in the 4 intervention districts and comparison districts from
Greatest decline observed in the 4 intervention districts that switched to OPs when there was vector resistance to PYs.

15. Questions? Thank you! www.pmi.gov www.africairs.net